Tires or wheels out of balance?
front steering
How are your: Tire balancing, alignment, steering stabilizer? And did the shaking occur right after the modifying of the suspension?
you need a front end alignment
FRONT SEATING AREA, DRIVER SIDE, UNDER DASH, MOUNTED ABOVE STEERING COLUMN.
Normally when you have a vibration at two levels, it is the wheels are out of balance on the front.
Driver's side firewall up above the steering column, in front of the power brake unit.
check your struts sounds like they are worn out
Out of balance wheel, damaged or faulty tire, bent or worn axle.
As looking at the front of the truck, on the right side of the motor above the power steering pump. Driven off the belt.
I would have the driveline u joints checked as well as the front end parts to start.
You most likely need to tires for the front of your car. You should replace your tires as soon as possible.
FRONT SEATING AREA, DRIVER SIDE, UNDER DASH, DRIVER SIDE OF STEERING COLUMN, MOUNTED ABOVE CONVENIENCE CENTER.